Three components make up fire fighting foam. Foam concentrate, water, and air are present. These three materials combine to form a foam solution, which has a lower density than water, oil, or gasoline and is a stable mass of tiny, air-filled bubbles.
Due to this special mixture, the foam solution is extremely fluid and easily covers fuel surfaces by flowing over liquid surfaces. It can rapidly put out fires, cool burning fuels, and cool heated surfaces.
The water supply is linked to the pipe system through an autonomously operated Deluge Valve, which starts the water flow. Automatic detecting devices that are mounted alongside water spray nozzles are used to trigger automatic actuation.
How does it works?
How Firefighting Foam is Generated?
Foam concentrate is based on hydrocarbon surfactants. They have different compositions:
- Synthetic firefighting foams:
- Fluorine-Free Foams (F3, also known as FFF): creating a foam blanket full of bubbles
- Fluorinated foams: Aqueous Film Forming Foam (AFFF) and Alcohol-Resistant Aqueous Film Forming Foam (AR-AFFF also called AFFF-ARC)
- Protein-base foams:
- Protein foam
- Film Forming Fluoroprotein (FFFP)
- Alcohol-Resistant Film Forming Fluoroprotein (AR-FFFP)
The foam solution, also known as the premix solution, is a suitable combination of water and foam concentration. A 3% ratio indicates that three parts foam concentration is mixed with 97 parts water to make one hundred parts foam solution. At the nominal concentration, a foam concentrate is designed to be efficient. As a result, proper foam proportioning is critical for foam performance and effective fire extinguishment.
The foam solution is then expanded with air in the foam generator to generate finished foam. This ratio is determined by the type of foam concentration or fuel used. When a foam concentrate is specified as 1 x 3, it signifies that the concentrate-to-water ratio on a hydrocarbon fire must be 1%. On a polar solvent fire, 3 per cent.
The final foam is a collection of bubbles that create a stable foam blanket that separates the fuel supply from the oxygen supply. It extinguishes fires and stops the emission of flammable vapours. The volume of the completed foam created by the premix solution is represented by the expansion ratio. It may have a modest, medium, or large expansion. It has a strong relationship with foam generation equipment.
The AFFF foam blanket is made consisting of a thin aqueous coating that spreads quickly over the fuel surface, isolating the fuel from the oxygen supply. Alcohol resistant foams (AR-AFFF and AR-F3), on the other hand, generate a polymer layer to effectively extinguish Class B polar solvent fires. It keeps the fuels from destroying the foam. A long drainage period ensures an effective and long-lasting foam blanket. The drainage rate is determined by how long the foam blanket remains stable and protects more than 75% of the surface from burn back
How to Extinguish a Fire with Firefighting Foam?
Firefighting foam is ideal for fire suppression. It is made up of a premix solution (a mix of water and foam concentrate) and air. It condenses into a stable foam blanket that spreads over the fuels and sticks to the surfaces. Some foams generate a layer over the fuel surface that traps vapours. The application of fire fighting foam concentrate stops fuel from coming into touch with oxygen, resulting in the suppression of the fire. It also has a great cooling effect and will keep the fire from rekindling.
Firefighting foam works in two stages to suppress a fire:
- Separation effect: the foam blanket limits combustible evaporation by reducing oxygen access to the flammable substance.
- Cooling effect: it takes a lot of energy to turn the water in the foam blanket into vapour. This helps to minimise or eliminate the energy required by burning. This water vapour cools the fire’s high temperature and prevents thermal radiation from exacerbating the flames.
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